The heart of a computer is a magnetic disk drive which typically includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and/or write heads over selected circular tracks on the rotating disk. The suspension arm provides a force that biases the slider against the surface of the disk. When the disk rotates, air is swirled by the rotating disk adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of the rotating disk. When the slider rides on the air bearing the write and read heads are employed for writing magnetic impressions to and reading magnetic signal fields from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.
An underlying goal in magnetic recording is to maximize the number of bits that can be written in a given area. With regard to write head design, this translates to generating the highest possible field magnitude together with the highest possible field gradient within a region. In traditional systems, bits are written in concentric tracks, and conventionally the magnetic pole width defines the track width. As these tracks become narrower, the pole width must decrease; unfortunately, this often results in a reduction of maximum field (because of the inability to scale the rest of the recording system accordingly). In shingled recording, this problem is addressed by writing tracks in an overlapping fashion, thereby removing the constraint between pole width and track width, as shown in FIG. 5. In FIG. 5, a head moves across the disk to write the tracks (1, 2, 3, 4). Each successive track writes over a portion of the previously written track (e.g., track 2 overwrites a portion of track 1, track 3 overwrites a portion of track 2, etc.). Thus, write heads designed for shingled recording can have a significantly wider pole than conventional heads. Also, the portion of the head that can affect the properties of the written track more than other portions is the corner 502.
In fact, previous shingled write head designs have basically been just conventional write heads with wider poles, as shown in FIG. 6. In FIG. 6, an air bearing surface (ABS) view of a portion of a conventional shingled write head, a shield 602 is wrapped around the pole 604, with a nonmagnetic layer 606 disposed between the pole 604 and shield 602. Also, a gap 608 is disposed at the trailing edge of the pole 604. While this is functional, further improvements can be made. Conventional heads are designed to optimize the entire writing side of their magnetic footprint. At the same time, the field must fall off fast enough such that adjacent tracks on both sides are not overwritten. However, in shingled recording, most of what is initially written is erased by the following overlapping track. Due to this design constraint, only one corner of the original footprint ends up being relevant, as generally shown as portion 502 in FIG. 5. Thus, the symmetric design of previous shingled write heads needlessly constrains the field.
Therefore, a write head capable of shingled writing that alleviates some of the problems encountered with conventional shingled writers and better concentrates the writing of the pole would be beneficial.